Typically, biopsy procedures are performed to obtain specimens of tissue from an internal organ of suspect for detection of disease conditions, such as cancer, and are of particular utility in determining the extent of the spread of the disease prior to the performance of surgery or therapy. Where, for instance, an abnormality is suspected in soft tissue organs such as the liver, spleen, pancreas, glands, etc., or where a growth has been located and it is desired to determine the nature and extent of the growth, a biopsy may be performed in order to obtain tissue specimens for laboratory examination. In general, biopsy procedures are preferred over the difficulty and trauma of exploratory surgery.
An instrument, commonly referred to as a trocar, employed for obtaining tissue core specimens comprises a small diameter long tubular cannula and a long thin sharp-tipped stylet located inside the cannula and movable relative to the cannula. The stylet may be provided with a specimen notch on its periphery near proximal tip of the stylet. The proximal end of the cannula may be sharpened.
The trocar is inserted through a small incision or puncture made in the skin and driven into the body until its sharpened end enters the organ of suspect. During this insertion stage of the procedure the stylet is positioned within the cannula so that no more than the sharp tip of the stylet is exposed; the specimen notch is covered by the cannula. Once the instrument has been positioned at the site for the biopsy, the cannula is retracted along the stylet enough to expose the specimen notch in the stylet. Soft body tissues will then prolapse around the newly exposed portion of the stylet and into the specimen notch, whereupon the cannula can then be advanced along the stylet to cover the specimen notch once again. This forward movement of the cannula cuts out a specimen of the prolapsed tissue, which specimen becomes retained in the specimen notch of the stylet. With the cannula still concealing the specimen notch, the trocar may then be withdrawn carefully from the target site. Thereafter, the cannula is once again retracted to expose the specimen notch of the stylet, creating access to the tissue specimen sample contained therein. If the physician desires to obtain multiple specimens from the same site, the cannula may be maintained stationary in its advanced position at the biopsy site while the stylet is withdrawn through the distal end of the cannula. This removal also exposes the specimen notch, so that the specimen may be removed therefrom. The same or a like stylet can then be inserted into the cannula, whereupon the above-described specimen collecting and removing procedure may be repeated to obtain the additional specimens desired.
Several problems can arise during employment of known cannula and stylet type trocar devices for tissue biopsy procedures. The known devices are often difficult for the surgeon to manipulate, especially when the target site is deep within the body, and the relatively long biopsy device must be guided and located inside of the body by radiographic imaging. Further, even though some trocar devices are provided with ring, bar or loop type grip means, it is usually necessary for the surgeon to employ both hands to manipulate the trocar, and often the surgeon requires assistance from another person to perform the cutting operation that obtains the tissue specimen. Difficulty in manipulating the cannula while maintaining the stylet in an exact position at the target site is further compounded in the instance of trocar devices which incorporate separate obturator means for covering the stylet notch, since such is an additional element which must be manipulated during the biopsy.
In all biopsies, it is desirable to perform the cutting procedure quickly in order to prevent the prolapsed tissue in the specimen notch from being displaced outwardly during advance of the cannula end along the stylet. Slow movement by the cannula might result in insufficient specimen being obtained. Manipulation problems arise because the trocar structure must provide for the cannula and stylet to be movable together as a unit, and to be movable separately relative to one another. While the cannula is being retracted and then advanced along the stylet, the stylet might inadvertently move also, which movement could result in an unsuccessful biopsy procedure.
Manipulation problems can arise when it is desired to obtain multiple tissue specimens from either the same target site, or from several depths among the same puncture tract. As has been pointed out above, after a specimen has been secured within the specimen notch, the stylet will be taken out through the distal end of the cannula to provide access to the tissue specimen reposing therein yet leave the cannula in place. Then the same or a like stylet must be advanced completely through the cannula. Because the stylet is quite thin and often is of considerable length, care must be exercised when retracting and advancing the stylet (within the cannula) in order to prevent bending of the stylet. A bent stylet might bind in the cannula. The stylet is supported over its entire length only when fully inserted within the cannula. This tends to make insertion and advance of the stylet in the cannula, during multiple biopsy procedure, a carefully done two-handed procedure. Complete retraction and reinsertion of the stylet becomes relatively time consuming and undesirable patient trauma might occur because the biopsy procedure cannot be performed quickly.
It is, therefore, an object of the present invention to provide an improved soft tissue biopsy instrument of the cannula and stylet type which overcomes shortcomings of prior art trocar devices, is reliable in operation and may be used with advantageous facility, and which is of simple construction and relatively inexpensive to manufacture.